


Cat Chaser

by MarcusRowland



Series: Supergirl Returns [12]
Category: DCU (Movies), DCU - Comicverse, Stargate SG-1, Supergirl, Supergirl (1984), Superman Returns (2006), The Avengers (2012), Young Wizards - Diane Duane
Genre: Cats, Gen, Podfic Welcome
Language: English
Status: In-Progress
Published: 2012-05-13
Updated: 2017-07-01
Packaged: 2017-11-05 07:23:46
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 16,469
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/403853
Author URL: https://archiveofourown.org/users/MarcusRowland/pseuds/MarcusRowland
Summary: <blockquote class="userstuff">
              <p>Supergirl Returns #12. It's surprising how much chaos a cat can bring into your life. Especially one that appears out of nowhere, and comes with its own dimensional portal... DC Movieverse / Avengers crossover - now with added Stargate, Young Wizards, and cats!</p><p>And added Director's Commentary!</p>
            </blockquote>





	1. Part 1

**Author's Note:**

> This is a DC Movieverse / DC Comics / Avengers (Movie) crossover. All characters belong to their respective creators, giant megacorporations of doom, etc. and there is no intent to infringe on copyright. The title is from a novel by Elmore Leonard.
> 
> It may help if you've read the previous story, Five Dates Supergirl Didn’t Enjoy… And One She Did, which introduces several plot elements, but it isn't essential.

"Miss Potts."

Pepper turned away from the New York skyline and said "Yes, Jarvis?"

"There is a cat in laboratory four."

"What sort of cat?"

"A small brown one. It does not appear to be of any particular pedigree or breed. If it was a dog I would call it a mongrel."

"You're a snob, Jarvis. Okay... make sure it doesn't get into anything that will hurt it, I'll be down in a second. Any sign of Tony?"

"Mister Stark is still en-route, ETA approximately eleven minutes."

Pepper descended to the laboratories and followed Jarvis' directions to a clear area, where one of Tony's industrial robots was keeping the cat busy with a laser pointer. She kneeled and said "Cut the laser. Hey, kitty."

The cat pretended to ignore her until she clicked her fingers, then it sidled towards her, and allowed her to stroke its ears and eventually pick it up. "Hey now, what's your name?" She noticed that it was wearing a collar, and looked at a small metal tag. "Pasadena Humane Society - My name is Streaky." On the back was a phone number.

"Jarvis, the tag has a phone number. I'm guessing it's a Pasadena area code, number 555 4389. That's odd..."

"It is. As you know, no Californian area includes 555 in the local dialling code."

"Where did he come from anyway?"

"I'm afraid I don't know. He appeared from under one of the work benches. I do not currently have a camera covering that area."

"Show me where."

The robot with the pointer beeped at her, then scooted across the floor towards one of the benches, as Jarvis said "I think we may have a problem."

"You're not kidding." Under the bench a vortex of rippling light, like a donut-shaped aurora about a foot across, hovered a few inches above the floor, inclined at about twenty degrees from the vertical. There was a scattering of earth below it. Through the opening she could see a slanted view of a neatly mowed lawn and some trees and bushes. She guessed it was a park or someone's back yard.

"The structure and signature of the energy field resembles that produced by the Tesseract... on a smaller scale, of course."

"Put me through to Tony."

"Hello, you have reached the helmet of Tony Stark, boy genius. Please leave a message. Beeeeep."

"Yeah, like that works so well. Tony, we have a problem."

"We're broke? You're pregnant?"

"Nope to both. But you do have a new baby here."

"What sort of baby?"

"Some sort of mini-portal, it's under a bench in one of the labs."

"Jarvis, give me some video... hey, cool!"

"It appears to be expanding," said Jarvis, "the diameter was thirty-two centimetres when I first saw it, it's now thirty-four point seven."

"Where is this in relationship to the original matrix portal?"

"Directly underneath it."

"The matrix generated its portal about a kilometre above the generator, can't remember the exact number."

"Twelve hundred and forty metres."

"About how far from it is the mini-portal."

"Approximately nine point seven metres below the generator."

"Give me a ratio between those distances."

"Ignoring the margin of error, the ratio of distances is exactly one hundred and twenty eight to one. By the way, the portal is now nearly forty centimetres across, and the rate of expansion is slowly increasing. It will intercept the floor and the surface of the bench in less than a minute. I suspect that it will damage them."

"Okay... I think it's a harmonic of the original portal, smaller and probably opens out somewhere a lot closer to home."

"We just found a cat that seems to have walked through from Pasadena."

"Pasadena California? How far is that... okay, can't see an obvious connection."

"It may not be this world's California," said Jarvis. "The phone number on its collar does not correspond to any local code in current use."

Outside Pepper heard a sonic boom, and braced herself for another argument with the FAA. Moments later there was a clatter outside and Tony ran in, wearing his usual slacks and a Discworld T-shirt, the glow of his arc reactor nicely centred under the disc.

"Cool portal! Where's the cat?"

"Are you suffering from some optical deficiency?" asked Jarvis.

"Here," said Pepper, holding up the cat, which looked at Tony in disdain.

"Great, let's see what makes him tick."

"Over my dead body."

"Don't worry, I won't hurt him, just a few sensors. Jarvis, is Pepper being horribly irradiated even as we speak?"

"If she were, I think that I would have remembered to mention it."

"That's a no, I hope. Anything weird about it?"

"It appears to be an ordinary cat. However, I'm detecting occasional anomalous quantum events."

"And?"

"I was under the impression that you were the genius."

"Did we see anything like that with Thor or Loki?"

"No. By the way, the upper edge of the portal is about to come into contact with the power line to the bench. Should I shut it down?"

"Go for it."

"Done. It will be several minutes before the bench collapses."

"Okay, is Bruce around?"

"He's on his way up."

"Good - I think we need to get this thing out of here before it brings down the building."

"That does sound unusually prudent. For you."

* * * * *

"I think we can move it," said Bruce Banner. "The trouble is that if we do, we may change where it opens too."

"You mean the dimension Loki's storm-troopers came from? That would be bad."

"Possibly, or maybe Asgard itself."

"Excellent! Let's try for sideways out of the window then up, say a few metres above the roof, that shouldn't be too tricky."

"How do we get Streaky home if we do that?" asked Pepper.

"Quickly," said Bruce. "I want to take some more readings, but the events we're seeing could be caused by quantum entanglement."

"What does that mean?"

"I'm guessing that the cat comes from a fairly close worldline, maybe there are only a few minor differences. If I'm right it exists in both worlds, and there's quantum entanglement between the particles of the two versions now it's in our world. That's not really sustainable, so the entangled particles will vanish randomly from one or another cat. Eventually both of them will be damaged so badly that they die."

"How long have we got?"

"At the moment it's slow, it'll be hours before there's any harm. Say twelve hours for real damage, eighteen to kill both cats."

"You've got thirty minutes," said Pepper. "After that he's going back."

"But.."

"Twenty-five. We are not going to hurt a cat."

"What happened to twenty-nine through twenty-six," asked Tony.

"Trying for fifteen?" asked Pepper.

"Fine," said Tony. "Bruce, I'll see to moving the portal, you see what you can find out from the cat, then give me a hand. Pepper, get the others in, if this goes horribly wrong we'll probably need backup."

* * * * *

Natasha dangled a small cuddly toy in front of Streaky's nose and made "good boy" noises, while Pepper stroked him and tried to keep him from moving from the focus of a small battery of sensors.

"Any luck with Selvig and his team?" asked Tony.

"They're at the Arecibo radio telescope in Puerto Rico," said Pepper. "They had a hurricane through there three days ago, communications are currently lousy, I can get you a voice link but that's about it."

"Keep it as an option, but we'll try to handle it without him."

"Okay," said Bruce. "I think that's about it. There's an escalating pattern of quantum events, I'd say it was the beginning of an exponential series, a cascade of decaying particles. Make it six hours to significant damage, ten or twelve to death."

"Call it entropic cascade failure. It'll sound snappier when we write the papers and file the patents. Anything else we can learn from our feline friend?"

"Not really. Natasha, gently toss him back through the portal, but don't put your hands too close, we don't want you to get sucked into the world without shrimp or something."

"Without shrimp?" asked Captain America.

"Obscure geek reference, don't worry about it."

Natasha said "хороший кот" and tossed him towards the opening. He hit the portal and hung in mid-air, then bounced off and landed on the workshop floor, yowling, his fur bristling with rage.

"That's weird," said Tony. "Someone get a broomstick or something, give the portal a poke."

"I think that there may be higher priorities," said Jarvis. "In four minutes the lower edge of the portal will intersect one of the girders supporting this floor. I think that this might have unfortunate consequences."

"Get it out of here," said Steve. "We can solve the cat problem a lot easier if the building isn't collapsing."

"Okay," said Tony. "I think I can give it a little nudge, maybe move it up a few inches. Everyone stand well clear." He tweaked a couple of settings on the jury-rigged assembly of electromagnets and lasers he was working on, and switched on the power. For a few seconds nothing happened, then the portal disappeared.

"Was that supposed to happen?" asked Steve.

"No. Jarvis, what the hell just happened?"

"The portal re-located."

"Dare I ask where?"

"Approximately twelve hundred and forty metres above the tower. It is now considerably larger, incidentally; I'd estimate four to four point two metres in diameter, and it appears to be leaking water."

"I'd better get up there and take a closer look."

* * * * *

"What do you see, Tony?" asked Bruce.

"Okay, I'm just coming up level with the opening now... same scenery as before, looks like the new improved portal just sliced through a water pipe on the other side. I make that a couple of liters a second."

"Okay, I've got it on the monitor. Seems to be a lot of interference though. Try firing a repulsor burst at the portal, see what happens."

"Okay... a low-power shot has no effect... let's take it up a notch." Tony fired again, with enough force to knock down a small tree. On the far side of the portal the ground erupted, forming a shallow crater, and earth cascaded through the portal and onto Tony.

"I'd say that about twenty-five percent of the force is getting through," said Bruce.

"Sounds about right," said Tony. "I wonder what would happen if I fired a... holy crap!" He flew back from the portal, and was narrowly missed by a blue car that sped through and began to plummet towards the roof. He dove after it and grabbed the rear fender, which promptly tore off the back of the car. His repulsors threw him back up towards the portal as he struggled to regain control.

About a hundred feet up the car started to slow, stopped, and rotated until it was more or less horizontal, then slowly descended to land on the roof. Tony landed as its occupants, a man and a woman, climbed out.

"Are you all right?" asked Tony.

"Apart from a missing fender," said the driver, an attractive blonde wearing jeans, running shoes, and a silky blue blouse. "I really wasn't expecting to run in to anyone up there. Oh, and hi, I'm Kara Zor-El."

"Dick Wing," said the passenger, a tall muscular brunet wearing a smart grey suit.

"Tony Stark."

"Hi. We're looking for Kara's cat."

"You have no idea who I am, do you?"

"Should we?" asked Kara.

"Just a second," said Tony, flipping open his visor. He lifted into the air, flew to his landing pad, and walked back towards them as the robotic arms stripped the armour from his body.

"That's amazing," said Kara. "How do you get the timing that accurate?"

"Genius, and massive parallel processing power," said Tony. "You're interested in engineering?"

"I'm studying it."

"And you've already built yourself a flying car? Look me up when you graduate."

"I'm pretty sure this isn't our timeline," said Kara, "so that might be kinda difficult."

"I'm certain of it," said Tony. "I'm pretty famous, so is my company. Stark Engineering. If you were an engineering student from around here you'd know me."

"Sorry," said Kara. "I guess it doesn't exist in our world."

"Okay. We've found your cat, if you'd like to follow me I'll take you to him. Jarvis, send a couple of the engineering robots up to fix their fender."

"Neat T-shirt," said Dick, "how do they get that glowing effect?"

"That would be me," said Tony, but didn't elaborate.

As they came down the stairs Jarvis said "Sir, I feel that you should be aware that the gentleman is carrying concealed weapons. Escrima sticks, several throwing stars, a small Taser, and something that looks like a grapnel gun, as well as various other devices. The young lady is unarmed."

"Now he tells me," said Tony. "Okay, is this going to be a problem?"

"Not unless you make it one," said Dick. "I'm just here to help Kara find her cat, we don't want any trouble."

"Neither do we," said Tony. "What are you? Cop, gangster, bodyguard?"

"Vigilante," said Dick.

"Okay," said Tony. "Just so you know, there are probably at least four people here who can beat you up without working up a sweat. I'm not one of them, so watch out because I'll cheat if I have to."

"I'm not here to fight."

"We just want to get Streaky and take him home," said Kara. "Oh, and shut down that portal thing if it's yours, it's chewing up my back yard."

"So how does the car fly?"

Kara smiled. "Magic pixie dust. I caught Tinkerbell and waved her over the engine."

"Do you mind if the robots look under the hood?"

"Knock yourself out."

"Everyone," said Tony, "These guys are Kara Zor-El and Dick Wing, they're here looking for Kara's cat. Kara's an engineering student, and Dick's in the vigilante business. Meet Natasha Romanoff, Clint Barton, Bruce Banner, Steve Rogers, and Pepper Potts."

"Hi!" "Pleased to meet you."

"Neither of you know any of those names?"

"Should we?"

"Okay, you really aren't from around here. That's weird, because if your time line is really distant we shouldn't be seeing quantum entanglement events, and your cat's showing them."

"Where is Streaky anyway?" asked Kara, looking around the room.

"Didn't you have him?" Pepper asked Natasha.

"I haven't had him since we tried to put him through the portal."

"That might be difficult," said Kara, "the last time I ran into a dimensional portal it carried a big energy charge, I think that there are sometimes big differences in potential between different dimensions. Coming here is like going downhill, but you might have to pump in a lot of energy to get back through it."

"That's why you needed the car," said Tony, "a Faraday cage to get you through the energy field."

"That and we needed transport. So... Streaky?"

"Who had him last?"

"Natasha had him," said Pepper, "then we moved the portal out of here in a hurry. Anyone seen him?"

"He's got to be here somewhere," said Bruce. "Wait a second, I can track his movements through his quantum signature. But I'll have to eliminate your signatures first."

"What do we do?" asked Kara.

"Just stay where you are while I calibrate the sensors... that's odd, neither of you is showing any significant entanglement events. Though I'm detecting some from the roof."

"What does that mean?" asked Dick.

"It probably means that you don't exist in this dimension, maybe some of the atoms in your body do, but less than I would expect. Which is odd because a doppleganger of your cat does, and your car does."

"That's quite likely," said Kara. "Dick is a refugee from another dimension, he's only been in my world for a few months. And if I'm around at all in this universe I'm probably a few light years away from Earth, wouldn't that prevent entanglement?"

"Yes, it propagates at light speed..." said Bruce, then said "Wait a second, doesn't that mean you're an alien?" 

Kara held up her hand in a Vulcan salute and said "klaatu barada nikto. Take me to your leader." Clint and Natasha watched her warily.

"You're an alien?" said Tony. "Why do you look human? Here to impregnate all the men with your flesh-eating eggs? Shape changer?"

"I wish, shape changing would be useful sometimes. No, Krypton was seeded by aliens who abducted early humans from Earth, about a hundred and fifty thousand years ago. Nobody's entirely sure why they did it, or why our evolution didn't diverge more, but we're not that dissimilar to Earth's humans. In fact my cousin married a woman from Earth, they have a kid."

"How did you get to Earth?" asked Bruce.

"A space warp a lot like your portal the first time I visited Earth, a spaceship the second. But that was a long dangerous voyage in suspended animation, it nearly killed me. I don't recommend it."

"Your people can do that and you're studying engineering? _Our_ engineering?"

"We're trying to introduce our science and technology to Earth, but unless we start out with Earth's technology and build on it carefully it might as well be magic, people try to use it without understanding it. That's already got people killed. One criminal idiot who thought he had a handle on it came close to destroying most of the eastern seaboard."

"Sensible policy," said Bruce.

"How do you stop people from helping themselves?" asked Clint.

"I'm just naturally persuasive," said Kara.

Behind her Dick raised his eyebrows and said "Riiight...."

"Now, about Streaky?"

"I'm on it," said Bruce. "The instrument readings aren't clear, I think he's got under the floor through the hole the portal made, but he's within thirty feet."

"Okay," said Tony. "Jarvis, use the systems I installed for cleaning out escaped laboratory specimens, but turn off anything that might hurt him."

"Laboratory specimens?" asked Dick.

"Intelligent slime moulds, things men was not meant to know, rats, that sort of thing. We're big on research here."

"What exactly is here?" asked Dick. "I was wondering, because this doesn't look like a commercial operation somehow."

"We're the Avengers," said Steve, "we're what the papers like to call a superhero team." It was obvious that he was uncomfortable with the term.

"We used to have some of those in my world," said Dick, "they can be fun, especially the Christmas parties, but they get a bit cumbersome if you get too many big egos in the mix."

"No argument there," said Pepper.

"There isn't anything like that in my world," said Kara, "though we do have some superheroes. Can you imagine Batman and Hancock on the same team?"

"For about ten seconds before they killed each other," said Dick.

"Do either of those names ring any bells?" asked Tony.

"No," said Natasha.

"I have the cat isolated," said Jarvis. "He is under the floor, grid reference G-11."

"Underneath the particle accelerator?" said Tony, checking the layout on one of the ubiquitous screens.

"Is there a problem?" asked Kara.

"It weighs forty-eight tons, it's bolted down, and we'd need to disconnect about sixty cables to move it more than a couple of feet."

"And?"

"The quantum effects he's experiencing might damage him by the time we can get it moved."

"Which would be bad," said Kara.

"Bad for him, certainly," said Tony.

"And for us." Bruce turned the screen to face them. "There's something I forgot, the energy release. The entangled particles don't just disappear, they annihilate each other. It's a cascade effect, starting very slowly but increasing exponentially. Say your cat weighs four kilograms, two kilograms would eventually be converted to energy. It's being radiated as neutrinos, which is why I didn't detect them at first, they tend not to cause problems. But in the last few seconds before the reaction completes a few hundred grams of matter will be converted to energy. Even as neutrinos we're talking a blast of several kilotons, possibly even worst."

"Two blasts," said Kara. "You said there must be a cat like Streaky somewhere in this world, probably in your version of California, he could be anywhere and the same thing would be happening to him."

"Bruce," said Tony, "we need to get him out of there now, and back into his own world. Can you do it without losing control?"

"No other option?"

"Not in the time we have available. Let me get suited up first."

"How long have we got?" asked Kara.

"My best guess is still an hour or so before he starts to get hurt, but I've revised downwards twice now."

"Kara..." said Dick. "Isn't there something you should be telling these guys?"

"I guess." Kara looked embarrassed.

"What exactly might that be?" asked Clint, suspicion in his voice.

"Well... it's probably easier if I show you. Can you cut the power to the particle accelerator?"

"Already done," said Tony, "I didn't want the radiation to hurt him."

"Okay," said Kara. She went to one of the massive anchoring bolts and gripped it between her fingers and twisted. The head tore off. "Oops."

"It's okay," said Tony.

"What Kara kinda forgot to mention," Dick said as she moved around the machine and removed or destroyed the bolts one by one, "is that Kryptonians are pretty strong."

"I'm getting that. What do you think, Bruce?"

"I'm jealous; the other guy could smash the thing if I hulked out, but I don't think I could do anything that delicate. Assuming I was in my right mind, of course."

"Okay," said Kara, dumping the last bolt on the floor a few seconds later. "how far do I have to lift it before you can get the floor panel out?"

"About a foot," said Tony.

"Can I do that without damaging the cables?"

"Maybe, not sure."

"Okay, let's give it a try." Kara bent her knees, put her hands under the main mass of the particle accelerator, and lifted. It went up, wobbling a little, until some of the cables were taut. The floor panel she was standing on dented slightly under her feet. "How's that?"

"Just a second," said Tony. "Steve, can you lift the next floor panel enough to slide it out from underneath?"

"Let me help," said Dick. The floor panels had recessed lifting handles; Steve and Dick grabbed them and pulled and the panel lifted up a little; straining as hard as they could they managed to pull it back a couple of feet before the cables got in the way.

"There he is," said Clint, pointing into the cavity under the panel. He reached in and tried to get a hand to Streaky, but there wasn't quite room for him to reach far enough through the narrow gaps between the cables.

"I've got this one," said Pepper. She kneeled by the opening and waved a small metal can towards Streaky. He snuffled and walked towards her, but stopped too far back for easy grabbing.

"Isn't that my caviare?" said Tony.

"It's a good cause."

"Can you hold the accelerator for another moment?" asked Natasha. "I think I can reach him now."

"I think so," said Kara.

"Good." Natasha dropped to the floor and squirmed under the cables, snaking her torso under the bulk of the generator, and grabbed Streaky. Clint pulled her out.

"Now just slide the panel back and put the accelerator down again and we're okay," said Tony. Everyone else glared at him.

* * * * *

"You've got the cat," said Bruce, "and I've modeled the wind flow around the tower, it looks like the water and dirt that's falling through the portal will be thoroughly dispersed before there's serious breakdown of its entangled particles. The mass won't be concentrated enough for the neutrino flux to do any damage."

"Are you sure you can shut the portal now?" asked Kara.

"Positive," said Tony. "The way it behaved when we tried to move it told me what we were doing wrong. I can shut it down completely."

"Have you guys got everything?" asked Clint.

"We've got Streaky, you've put all the earth that you could vacuum up into the trunk, and I don't think we've left anything behind."

"Once this closes we probably won't be able to reopen it into your dimension," said Tony, "I'm pretty sure it linked to it randomly. Make sure you have all your belongings."

"We're fine," said Kara. "Buckle up, this is going to be a bumpy ride." She fastened her seat belt and started the engine; Tony noticed that the belt seemed to be thicker and stronger than a regular belt, and guessed that it had something to do with her strength. Dick waved, and the car rose into the air, wobbling slightly, and ascended in a spiral towards the portal.

Tony followed, all of his instruments trained on the car, looking for an energy signature that might explain how it flew. There was some sort of hyperspace flux, but he couldn't imagine how any so-called pixie dust could generate the effect. Maybe nanobots? There was something about the way the car was flying that seemed a little off to him, but he couldn't quite figure it out. "Jarvis, did you find anything unusual in the engine compartment?"

"No, just standard components."

"What about the 'Magic Pixie Dust' she mentioned; any nanobots or strange chemicals, or the sort of energy signature we got from Asgard technology."

"No sir. I believe that she may have been joking."

Ahead the car wobbled again and banked for its final approach to the portal, and hit the boundary at about 50 MPH then slowed as though it had run into something soft but strong, coming to a halt with the front two thirds in Kara's world, the rear wheels and trunk in Tony's, with the car's suspension caught on something. Tony flew up and pushed up and forward on the rear fender; the car lurched forward and back into Kara's world, and he stopped himself before following it and hastily backed off from the portal. Through it he glimpsed Kara and Dick get out of the car. Kara waved at him, and he waved back, then said "Bruce... shut down the portal."

"In five... four.. three... two... one..." There was a bright flash and the portal was gone.

**Epilogue**

"Just when exactly were you planning to tell me about your visitors?" asked Nick Fury.

Tony smiled at the screen and said "Why tell you? You've got bugs all through the tower, you knew as soon as I did."

"Did it occur to you that I might have experts who could help?"

"Really? You know someone who knows more about portals than my team?"

"Yes. Reminds me, you probably can't patent anything derived from entropic cascade failure. There are already several classified patents in that area."

"Tell me more."

"You don't have the need to know. Now about the alien... do these Kryptonians pose a threat?"

"She seemed okay, but she said their technology nearly destroyed the eastern seaboard. And she was really strong... maybe Hulk strong, without the turning into a green rage monster part. One reason why getting them out of here quickly seemed the best way to handle things."

"Any other abilities? And did you get anywhere on the flying car?"

"Yes to both. There was something odd about the way that car flew, I analyzed the video and eventually realised that when it changed direction it was pivoting around the driver's seat, not the car's centre of mass. The car wasn't flying, she was, she just brought the car along to give her boyfriend a ride. I'm still figuring out how it works, but with luck it's something I can duplicate. Knowing that it's possible is a good start towards a solution."

"Interesting..."

"Now if there's nothing else, I need to make sure that Jarvis has flushed out the last of the cat poop from under the lab floor. We've got about twenty minutes before the cascade really gets started, I'd really like to make sure it's well clear of New York and harmlessly diluted first."

"Carry on. Fury out." His picture disappeared, replaced by a picture of Natasha holding Streaky captioned 'I has a Natasha.'

"Asshole," said Tony.

"He can still hear you, you know," said Pepper.

"And he's still an asshole. Now, about that cat poop..."

* * * * *

"They seemed like nice guys," said Linda Lee, as they walked back into her house. "Maybe we could have given our civilian names. But there were one hell of a lot of weapons around that building, and cells even I might have had trouble getting out of. And cameras everywhere, it was like _1984._ If we do exist in that world, I really don't want them knocking on our door."

"I think they were a government-sponsored superhero team," said Dick Grayson. "I've never heard of one of those that ended well. Stark and Banner were their scientists, I'm guessing that Barton, Romanoff and Rogers were muscle. Rogers was pretty strong, well over normal human levels, all three of them moved like they had combat and martial arts training."

"I've seen Romanoff's picture in our world. She's on the 'Ten Most Wanted' wall at NCIS headquarters, arms trafficking and murder. I don't know any of the others."

"Give the names to Bruce... our Bruce... maybe he can track them down."

Outside Streaky yowled, and Linda's dog started to bark. "Now what?"

Another portal was opening a few feet above the lawn. As they watched a man fell through and landed, crouched, on the lawn. The portal slammed shut, and the man stood, a bearded blond giant holding a huge hammer, and said ""Well met, fair maiden. I am Thor. Couldst thou tell me whether this be Midgard, and where I might find the abode of those known as the Avengers?"

"Now that might be tricky," Linda began. She had a feeling it was going to be one of those days...

**Notes for the Chapter:**

> Entropic Cascade Failure is stolen from Stargate SG-1. I've changed its effects considerably, the technobabble shouldn't be taken too seriously. The World Without Shrimp is a Buffy reference; in this universe (which has Buffy crossovers in previous stories) it is presumably a common philosophical concept. Natasha's Russian means "Good cat." Thanks to EllandrahSylver who gave me Thor's dialogue when I wasn't quite sure how to talk like an Asgardian.


	2. Part 2

**Notes for the Chapter:**

> I hadn't originally intended to follow up on the ending of Cat Chaser, but by popular demand...
> 
> This is a DC Movieverse / DC Comics / Avengers (Movie) / Stargate / Young Wizards crossover. All characters belong to their respective creators, giant megacorporations of doom, etc. and there is no intent to infringe on copyright. This is set after the Avengers movie and between Seasons 8 and 9 of Stargate SG-1, and at no particular point in the Young Wizards series. Note that this is not exactly the same Stargate universe as the TV show; it's canon that there are numerous parallel universes with similar Stargate projects. The main difference is that America was governed by the Bartlet and Santos administrations, and Senator Kinsey never became Vice-President, though he still has enormous political influence. A reminder, again, that for the purposes of this story entropic cascade failure works a little differently than in Stargate canon.

Lieutenant-Colonel Samantha Carter checked the reading on her GPS and drove her Harley off the road and into a picnic area a few miles from Area 51. It was already evening, and there was nobody around, no sign of the contact she expected to meet.

"Good evening."

Sam spun round, startled, and saw a blue and red figure dropping down from the sky. "Supergirl?"

She landed on the asphalt a few feet from Sam. "Call me Kara. Doctor Carter, I presume."

"How did you know that?"

"Sorry, I forgot; The password is Xenon."

"One down from Krypton on the periodic table... of course! The countersign is 'Tellurium.' General O'Neill said I'd be working off the record for a few days, he didn't say it would be with you; what's this about?"

"It's probably going to be easiest to explain this when we reach our destination. If you'd like to get your bag and lock your bike, I'll fly you there and come back for the bike in a few minutes."

"Where are we going?"

"California."

"Okay..."

Five minutes later Sam was trying to get her breath and watching Supergirl fly off again. She looked around, and realised that she was standing outside an odd structure that seemed to consist of a couple of dilapidated-looking trailers, apparently joined together, with a lean-to attached. There was a spectacular view downhill and out to sea to the west; she recognized a coastline she'd flown over many times, and realised that they were somewhere on the hills inland of Malibu. She could hear a little noise from inside, it sounded like a football game on TV. A man's voice said "Good evening. Quite a trip, isn't it?" 

Sam thought she recognized an East Coast accent, probably Gotham City. "That was awesome, but travelling through atmosphere at that speed without any streamling or protection should have torn me apart, burned me, and killed me about a dozen different ways, how the hell does she do it?"

"Ask her when she gets back, I'm sure she'll be happy to tell you." She peered into the shadows, and saw a figure in a dark costume and black domino mask, who said "Welcome to California. I'm Nightwing."

Sam searched her memory, and remembered a news report about a new superhero fighting crime in San Francisco. "Okay... Is this some sort of superhero clubhouse?"

"You could call it that, maybe. It's Hancock's old home; he used to live here before he moved to New York, hasn't got around to selling the land yet. He's letting us borrow it for a few days. If you'd like to come inside I'll show you your room."

"What's this about?"

"We were looking for the best scientist to help us with a problem," said Nightwing, leading her inside. "Kara ran a computer search, it turns out that fifteen out of eighteen papers that discuss related topics refer back to a couple of your theoretical papers, and to a thesis written by a student who dropped out of sight in the nineties, we haven't been able to locate her. The other three missed a key phrase that we knew was pretty important; entropic cascade failure. So she called in a few favours, and someone must have cut some orders for you."

If they knew that phrase there was no point beating about the bush. "You have a problem with parallel worlds?"

"A portal to one opened two days ago, we both visited that world's New York. Fortunately the people on the other side knew a lot more about portals than Kara and I do; we got back and they were able to shut it down."

"So what's the problem?"

"About five minutes later another portal opened, and dumped out someone who was trying to reach their dimension; we're guessing that somehow the earlier portal switched him here. We can't figure out how to send him home."

"If he's been here for two days cascade failure would have killed him by now, if it was going to."

"It's not that simple, unfortunately."

"It never is."

"To start out with the biggie, he's a god..."

* * * * *

"Okay," said Sam, staring at Thor. "So... you're a god..." He certainly looked the part, a bearded giant larger and blonder than the hologram she'd once met, and with a much bigger hammer. A tiny part of her mind was speculating about the size of the hammer and other attributes, she resolutely tuned it out. She wondered what the Thor she knew would make of the newcomer, if they ever met.

To one side she saw Nightwing grin, and suspected that he'd spotted the _Ghostbusters_ reference.

"I am Thor," he repeated. "Thor Odinson of Asgard. You may call us gods if it pleases you; we are what we are. I have crossed the Bifrost Bridge to join my battle-brothers the Avengers and my beloved Jane. Belike this world is another Midgard separated by a chance of fate, our wise men spoke of such things."

"Did your wise men ever say what to do if you ended up in the wrong world?" 

Thor shrugged. "Summon the Bifrost Bridge, return to Asgard, and try again. But I have no way to summon the Bridge, and if Heimdall is looking for me or my signal it may be in the wrong world."

"That's our main problem," said Supergirl, back from moving Sam's bike. "The other is that if Thor eats or drinks much in this world the atoms will end up as part of his body, and entropic cascade failure would destroy them when he gets to the timeline he's after."

"That's a possibility, of course."

"I'm not sure what happens when entropic cascade failure goes to completion," said Supergirl, "in the Avengers timeline they were detecting neutrinos and said there could be a nuclear explosion if there was a lot of material involved, but even a little might do enough damage to wreck his brain."

"Okay," said Sam. "I can certainly agree that sort of damage seems probable." She didn't want to admit to having seen it. "I'm not so sure about the explosion." But she'd never thought to check for neutrino emissions, the basic equipment for that was a huge array of light detectors in an underground tank full of heavy water, not something she could whip up out of junk in the lab.

"There is a simple answer," Thor said patiently. "Those who crafted Bifrost were wise in such matters; if I return to Asgard before venturing to Midgard again all will be well."

"That sounds good if we can do it," said Nightwing, "but it might end up that we have to send you on to the world you were originally headed for."

"Then if you are right about the dangers of eating here, my fast must continue." He sighed.

"Whatever happens," said Sam, "I'll need to run some tests at the site where the portal appeared, and I'll need some equipment."

"Here's a list of the equipment STAR Labs in Metropolis think might be useful," said Supergirl, "take a look at that and let me know what else you want. There is one problem with the site..."

"Yes?"

"It's a friend's back yard. If it becomes common knowledge that I visit there she'll never have any privacy again. She's already had one incident that nearly ended badly, so she's a little worried about attracting attention. I'll get your equipment there overnight, I can fly it in without anyone noticing, but tomorrow we'll need to travel in plain clothes, and I'll have to disguise myself a little."

"I have no problem with that, I've worked undercover before, and I was warned I'd need civilian clothes. The thing that bothers me is that we may be trying to open a portal to another dimension. What if something we don't like tries to come through? Can we get military support quickly?"

Supergirl raised an eyebrow. "Military?"

"With respect... I know that you're tough, but if something hostile comes through that knows about Kryptonite you'll be in trouble."

"Fair point... Well, Thor is pretty tough, and before we start I'll call Hancock and ask him to be ready to lend a hand if needed. He's not affected by the stuff. Now then, tell me what you'd like to eat, and I'll go get some takeout. While I'm gone, take a look at the list."

* * * * *

"If I've got this right," Nightwing said an hour later, helping himself to the last of the beef in black bean sauce, "there are a few key time lines, and everything else reflects them to some extent. Asgard is one of the biggies, and it's made it into the mythology of a lot of the parallel worlds. Did you ever come across a book called _Nine Princes of Amber?"_

"Don't you mean _Nine Princes_ in _Amber?"_ asked Sam.

"Not in the universe I come from, I'm pretty sure it was 'of.' Anyway, the version I read had a world called Amber, an archetype that everything reflected, thousands of near duplicates, and an infinity of worlds that were less and less like the original. The world I come from is pretty similar to this one, but we had different presidents, Atlantic City was called Bludhaven, and there were a lot more superheroes. It was different enough that I didn't suffer entropic cascade failure, though that might be because I was never born in this universe."

"That wouldn't be enough. All of the atoms in your body would probably be around in this world in one form or another."

"Then the magic that got me to this world must have protected me, the same way that the Bifrost bridge protected Thor."

"Magic," Sam said flatly.

"It exists. I knew several people who could use it in my old universe; I've traced one of them here, but he's in Britain and I really don't like him anyway, too many people seem to get killed when he's around. Kara knows some people, but for some reason they didn't want to get involved. I got the impression that the last time they opened a portal it ended badly."

"I'm a scientist, it's just difficult to take the idea of magic seriously."

"Science is magic that you understand," said Thor, suddenly taking an interest in the conversation, "and magic is science that you don't understand."

"Thanks, Yoda," said Nightwing.

"That is not my name," said Thor, "nor like this do I speak." Suddenly his voice was a near-perfect imitation of Yoda. "Foolish you are to mock the stranger's ignorance. Reflect you should that I have visited Midgard before."

"You've seen _Star Wars?"_ asked Sam, imagining Thor and Teal'c watching the movies and comparing notes.

"All three sagas," Thor said in his normal voice. "Stark insisted."

"They made three prequels in my world," Nightwing said gloomily, "it wasn't a good idea."

A little later Supergirl came back to the camper and said "I've got everything organized, Kal-El and I will collect the STAR Labs shipment in a couple of hours. They didn't have the full spectrum analyser you wanted, but WayneTech have one in their warehouse, they can have it ready for collection a little later." She helped herself to some vegetarian noodles and tofu, and warmed it with heat vision for a fraction of a second.

"How did you get WayneTech to do that?" asked Sam. "It usually takes about ten days from order to delivery."

"My cousin launched some satellites after Luthor's pulse damaged the new shuttle, WayneTech was one of the companies that benefited. They were happy to return a little of the favour."

"Well, that's not an approach I can take, I guess."

"If it's important contact me, I'll see what I can do to help."

"How do I do that?"

"I'll give you my phone number."

"You have a phone?"

"How did you think my friends get hold of me? Shouting 'Help, Supergirl' doesn't cut it if I'm on the other side of the world."

"Okay, thanks."

"I shall sleep," said Thor, "belike you will wake me if there is need." He went off towards his bedroom.

"Poor guy's really hungry and thirsty," said Nightwing. "He can apparently hold out much longer than regular humans, but it must be hard on him watching us slurp noodles."

"I know," said Supergirl, "but we'll head off early tomorrow, and get started as quickly as we can, try to get him back to Asgard before he's forced to eat. That reminds me, Kal-El told me a weird story while Star Labs was checking their inventory; while he was off Earth a few years ago he ran into a spaceship operated by an alien called Thor who said his race were called the Asgard and came from another galaxy. But they were little grey guys with big eyes, looked like the aliens in Weekly World News."

"I think those guys invaded my world one time," said Nightwing. "No, I'm wrong, they were the ones that wanted to buy Superman from the Justice League, offered a pretty decent price too."

"I'll have to tell him that. Maybe he had a narrow escape."

"Maybe they're one of the shadows you were talking about," suggested Sam, wondering why the Thor she knew had never mentioned meeting Superman. "If Asgard really is as important as you say there might be timelines that echo aspects of it in some way."

Kara finished her noodles and said "I want to fly a quick patrol along the coast before I meet up with Kal-El. Nightwing, do you want a lift back to San Francisco?"

"No thanks, Kara. Things are quiet there, and you'll need me to help out tomorrow morning, I should get some sleep. If you could stop by my place and pick up some civilian clothes for me, I can crash on the couch here."

"Okay. I'll be back about seven tomorrow, my friend's house is an hour or so by road from here. It might be a good idea to head off early and beat the traffic."

After she left Sam yawned and said "So... you and Supergirl?"

"What about us?"

"Did I detect a little spark there?"

"It's... complicated," said Nightwing. "There was a Supergirl in my world, but she took off to the thirtieth century with her boyfriend. I'm still getting to know this version."

"But you like her," said Sam, "You call her Kara without having to think about it, and a couple of times I think she caught herself before she used your real name. I'm pretty sure she likes you."

"And?"

"And nothing. I'm just saying... you have a lot in common, you could do a hell of a lot worse."

"No argument there."

"Let's get some sleep."

* * * * *

The following morning Sam was dressing when she saw a shadow pass her window, and looked out to see Supergirl landing outside, carrying a blue Honda Accord. She put it down and reached in for two flight bags, and walked out of view. When Sam came out of her room Nightwing was pulling on a casual suit, his costume and mask on the couch. Kara said "Do you mind if I change in your room?"

"Help yourself," said Sam.

"'Morning." Nightwing finished adjusting his tie and started to transfer equipment from his costume to concealed pockets in his suit.

"I'm surprised you let me see your face. Isn't it a secret?"

"Not if you don't recognize me. I had to be more careful in my old world, I was in the papers occasionally under my real name. Here I'm just another face in the crowd. Oh, and for today's purposes my name is Richard Wing, call me Dick, and Kara is Kara Thrace."

"Someone likes Battlestar Galactica."

"In my universe they didn't reboot the show. I've been catching up, but I think I prefer Firefly, though the fourth series kind of sucks."

"Okay," said Sam. "Where's Thor?"

"Out back, he's meditating or praying or something, not quite sure."

Kara came back out, carrying one of the flight bags and wearing jeans over the lower half of her costume, and her usual boots and top with the 'S' insignia. Her cloak was removed, her hair tied in pigtails, and her eyes, probably her most recognisable feature, covered by mirrorshades. A red leather jacket completed the outfit. With one exception it was a surprisingly effective disguise.

"Isn't the 'S' a little obvious?" asked Sam.

"Not really - the Superman Foundation licenses the logo to at least eight clothing companies, if you go into town you'll see plenty of people wearing it. My top's a little tougher than the others, of course." She turned to Nightwing. "Linda let me borrow her car; would you mind driving?"

"Okay. You'll have to give me directions; I've never been there by road, you've always flown me."

"Neither have I, but she left her satnav in the car, it's set for her house."

"Okay. We can pick up some coffee on the way."

"Get shawarma," said Thor, coming around the house carrying his hammer.

"You know you mustn't eat," said Sam.

"It smells good, I will enjoy that."

"It's too early in the morning for greasy food," Sam said firmly. "We'll get some cinnabons, they smell terrific."

"We should be at Linda's place in an hour or so if we don't waste too much time," said Kara. "It's clouding over a little, I hope that we aren't in for a storm."

* * * * *

"I'd better warn you about Linda," said Kara, when they were on the outskirts of Pasadena, and Thor was dozing in the front passenger seat next to Nightwing. "I've known her since my first visit to Earth, and she's helped me out a lot in getting to know Earth's culture, but she's a total fan-girl."

"Fan-girl?"

"She keeps Supergirl scrapbooks and memorabilia, and looks enough like me that she came third in the Malibu Beach Miss Supergirl look-alike competition last year. She wanted to buy red cloaks for her puppy and her cat to celebrate, but I managed to talk her out of that."

"She sounds like a ditz."

"She's actually pretty bright," said Nightwing. "Did you ever see adverts for a range of science toys called 'Linda's Laboratory?'"

"I gave a couple of the starter packs as Christmas presents last year. She's that Linda?"

"The one and only. She got into toys to encourage more girls to take an interest in science, that ended up paying for her house."

"Can't wait to meet her."

A moment later there was the faint buzz of a vibrating phone, and Kara dug into a jacket pocket and produced a late-model iPhone; she glanced at the screen and said "Speak of the devil, that's her now," and listened for a moment. Sam could hear someone talking excitedly, but couldn't make out the other person was saying. "Are you sure..? She did what..? That's a little rough on him, isn't it..? Okay... Okay, I'll talk to you later. Bye!" She turned back to Sam. "Okay, it sounds like the meeting's postponed, she's had to run out, some sort of crisis with one of her friends and her boyfriend. She's left the key for us and says there's coffee in the pot, she'll be back this evening."

"Okay. By the way, I suppose you know that iPhones can be tracked pretty easily if someone knows how to hack the phone company."

"If it was an ordinary iPhone I'd be worried. This one is actually a Batman special. Works anywhere in the world, completely untraceable."

"You've met Batman? What's he like?"

"He's Batman," Kara and Dick said together, then both laughed.

"It's an experience," said Kara. "He's always five steps ahead of you, ahead of anyone. Once he managed to sneak up on me and Kal-El, and that's not exactly easy."

Dick signalled a turn. "I worked with him for about eight years in my world. The one I knew was older and looked completely different to the one here, but the attitude was identical. Total dedication to fighting crime. You remember we were talking about archetypes last night, key timelines that are reflected in hundreds of others? The magician that sent me to this world pretty much said that Batman and Superman are that important."

"Not me?" Kara asked sweetly.

Before he replied the satnav said "Turn right." He turned the corner, paying no attention to a tall pedestrian wearing jeans, glasses, and a Metropolis University t-shirt who was walking a white puppy the way they'd come. The Satnav said "You have reached your destination."

"Saved by the bell," said Dick. "Which house?"

"Up ahead, the bungalow right at the end where the road dead-ends."

"Are we there yet?" Thor asked sleepily.

"Just stopping. Kara, should I drive into the garage? I think there's a remote on the key-ring."

"She usually leaves it under the car-port, I think."

"Okay."

"When we stop stay in the car while I make sure that nobody is watching us."

Kara got out and looked around for a moment, then said "All clear. None of the immediate neighbours seem to be at home. Linda said she hid the key where I can easily find it, I guess that means use X-ray vision."

"Start with the grey rock in the flower bed to the right of the door," said Dick.

She glanced at it then picked it up and twisted it open to reveal a cavity containing the key, and unlocked the door. "How did you know?"

Dick followed her into the house, with Thor and Sam bringing up the rear, "There's a couple of companies make those hollow rocks, they usually use sandstone or those grey layered river stones, forget what the rock is called, because they're easy to cut and drill, but they stick out like a sore thumb in areas like this where the native rock is different. Thieves know to look for them."

"Warn Linda when she gets home."

Inside the house was tidy and seemed entirely normal, and smelled of furniture polish and freshly-brewed coffee. Kara led the way to the kitchen, saying "She can't have been gone for long." The coffee machine was still gurgling and dripping. "Anyone want a cup?"

"Yes please," said Sam, "but let's make it a quick one, we've got work to do."

"All of the equipment is out in the yard and on the back porch. We could have it out there."

"I'll make it," said Dick, "I think I remember where Linda keeps the cups. You guys go play mad scientist."

"Good idea," said Sam. "Okay, Thor, Kara, can you come lend me a hand? I'll probably need to move things around a bit to get the equipment set up."

"You might want to start by testing Linda's cat," said Kara, "he was in that world longer than either of us."

"Where is he?"

Kara looked around for a moment, then said "Sunbathing on top of one of the packing cases outside."

"Let's get to work."

* * * * *

"You are a wise cat, Streaky," said Thor, rubbing the cat's stomach with a massive finger. Streaky stretched, purred, and licked his other hand with a rasping tongue. "He likes me."

"My impression of that cat," said Kara, assembling scaffolding and attaching sensor antennae as Sam directed, "is that he likes anyone who'll scratch his ears or give him a belly rub or cat food. I wouldn't read too much into it."

Sam looked at the readings from the instruments that were already on line and said "I'm getting a very faint entropic decay effect from the cat, but he's in no risk of cascade failure. My guess is it's just the last residues of air from that dimension, maybe he ate a little food or drank a little water too."

"Is it enough to give you a fix on their dimension?" asked Dick, who was unpacking more instruments.

"No. The readings from you two are even fainter, you said you weren't there nearly as long."

"And we didn't eat or drink at all. So what's the plan?"

"I'm getting nothing from the first portal you described, the one that leads to the world you visited. I think we can forget sending Thor that way, so he might as well eat. But I am picking up a very faint trace from the second portal, the one Thor fell through. I'm thinking that if we can pinpoint its location and I can get more of a feel for the energy configuration we might be able to do something."

"Such as?"

"Thor, you said that Heimdall would be looking for you in the world you intended to visit, right?"

"That is so. But by now he will know that I am not in that Midgard, or have somehow been hidden from him. He may be trying other worlds, but there are so many. It might take him weeks to find me."

"Okay... so what we need to do is attract his attention somehow. The way I figure it, we probably can't get your bridge without the right authorisation code, or whatever he uses, but we should be able to open the portal just enough to send some sort of signal, something to let him know you're here. Why don't you go get something to eat, and I'll try to think how we can do that."

Thor smiled. "I could eat an ox."

"I think Linda said something about burgers," said Kara, hovering in mid-air and adjusting an antenna. "Check the fridge, she's probably got stuff ready."

"I'll help," said Dick, "I'm not sure Thor knows much about burgers, and Kara can get this done faster anyway."

"Truly," said Thor, "I know nothing of this burger beast. Are they like oxen?"

"Kinda. Come inside, I'll show you." He and Thor went back into the house, tailed by Streaky.

"Linda shouldn't mind," said Kara, "I warned her that Thor was pretty hungry." She looked up at the sky, and added "More clouds coming, I think we might be getting some rain."

"I hope you remembered tarps to keep water off this equipment."

"I'll set them up next."

* * * * *

An hour later they were all in the kitchen, while light rain showered down outside. "So..." said Thor, eating his third burger, "Is there a way to call the Rainbow Bridge."

"Not with the equipment I have here," said Sam. "It would take megawatts of power, and megawatts more to send the signal."

"How big a generator are we talking about?" asked Kara.

"Say the output of the Hoover dam."

"Okay, not something I can easily bring here. How long would you need the power for?"

"Just a fraction of a second."

Thor smiled. "I think perhaps you forget who I am."

"Oh... right. Can you do something without damaging Linda's house?"

"Mayhap." He touched the haft of Mjolnir. An electrical nimbus flashed from the head, and the lights dimmed momentarily.

"Better not do that again indoors," said Kara. "Let's get out there and set things up, then I think we're in business."

* * * * *

Ignoring the steady drip of rain, Kara reassembled the scaffolding as a pylon; its tip, exactly where the portal had opened, bore a complex array of coils. Kara drove a dozen earthing rods deep into the ground, and Thor and Dick hastily connected them to Sam's equipment. Then Kara moved everything that wasn't needed as far from the portal as possible, and made sure that Streaky was inside the house.

"Okay," said Sam, "We'll need a short burst of power to open the portal a crack, then a lot more to send the signal. Does everyone know what they need to do?" Everyone nodded.

"Kara, Thor."

Kara flew up into the clouds, and Thor somehow threw his hammer and flew up with it to follow her. They vanished from view, and moments later there was a crash of thunder and a sheet of lightning rippled across the sky. Then another and another, and the rain became a torrent. Up above, Kara was cooling the cloud with her breath, while Thor summoned the lightning. After a minute or so they plummeted down again, and Thor said "It is ready."

"Okay," shouted Sam, "Dick!"

Dick climbed the pylon, raised his line-throwing gun, tethered to the top of the pylon, and fired its steel line and grapnel up into the sky, then dived clear and rolled to get away from the pylon.

"Thor!"

Thor raised Mjolnir and discharged another blast of lightning into the cables. Lightning surged into the pylon and up Nightwing's line into the sky, to be met by a massive bolt from the clouds. The bolt surged down, hit the coils at the top of the pylon, and left a swirling vortex of electrical energy, a ball of lightning a foot or so in diameter.

"And Kara! Then Thor again!"

Kara unleashed the full power of her heat vision, and for once it could be seen as a literal trail of fire, where even the air burned. It hit the portal and vanished. She began to fly in circles around the pylon, continuing to play her heat vision on the portal, while Thor sent another bolt of lightning into the portal, then another and another. Abruptly the vortex vanished, revealing the half-melted scaffolding.

"Did it work?" Dick shouted as the storm slowly died down. They could hear car alarms, and Sam hoped that nobody's house had been damaged by the downpour.

"I have no idea," Sam shouted back. "The instrument readings aren't clear. We definitely had a rift, for about eighteen seconds, but there's no guarantee Heimdall saw it."

"Can we do it again?"

"I'd rather not risk it just yet."

"I think we're okay," said Dick, looking back towards the pylon. While the rest of the yard was gloomy under the clouds, the scaffolding and the area around it were awash with multicoloured light, a vertical path of light.

"Okay," said Dick. "If the bridge works the way you think it does, these should be safe to take to the Avengers world. Give them to Stark, he should know what to do with them." He handed Thor a paper sack.

"Thank you, my friends!" Thor clasped Dick's hand, and briefly hugged Kara and Sam, then strode into the light and vanished into its brightness. A second later it was gone, and so was he.

**Epilogue 1**

Kara flew off with Sam and the precious data tapes, headed for STAR Labs and their computer analysis suite. Dick waited until they were out of sight, then picked up his phone, hit speed dial, and said "Okay, Clark, I think the show's over here."

A couple of minutes later Dick heard a dog bark, and went to the front door to let in Clark Kent, still wearing his Metropolis University T-Shirt, and Linda's dog. "Did everything work?"

"I think so. It really looked like Linda had only just gone out, I don't think Carter suspected anything. If she had, I think she would have looked for a timer, not someone switching on the coffee machine just before we arrived."

"Simple illusions are the best. Anyway, I'm sure Linda could have coped without me. The first time I visited Lois's apartment, I must have switched from Clark to Superman five or six times, she never suspected a thing."

"Reminds me, thank Lois for making that call. We may have to do more of a quick change act if Carter comes back to meet Linda, but here's hoping it doesn't happen. Thanks for all your help."

"My pleasure."

**Epilogue 2**

Sam watched as a dozen streams of data slowly built up a complete picture of the portal's creation. There was no doubt in her mind that she could duplicate the effect with enough power and the right equipment. There were obvious dangers, of course, but it looked like she might have a safer alternative to the quantum mirror.

There were still some unanswered questions, of course, not least why the portals had opened in Supergirl's friend's yard, of all the places in the world. She hadn't seen anything in the house to explain it, that didn't meant there wasn't anything there to find. She made a mental note to keep an eye on Linda Lee's career, and anything that might explain the mystery.

**Epilogue 3**

"Okay," said Tony Stark. "This stuff is gold. We need to make deals with all of the actors, writers and production companies. At least half of the Firefly episodes are completely new, about a third of Galactica, and I've never even heard of Wormhole X-Treme. We're sitting on a fortune."

"Methinks," said Thor, "they were intended as a gift for us, recompense for the trouble caused by the cat. They were meant for us to enjoy. To think only in terms of profit is..."

"Good business sense," Tony interrupted. "Don't worry, we'll get to watch them first. Can't wait to see how this version of Firefly handled the time travel and alien contact story arcs..."

**Epilogue 4**

Mmmur'rr, whom humans called Streaky, waited until Linda and Dick were asleep before he slipped out into the night and waited for the rest of his team to arrive.

"Well?" said R'rrath, a grey Saimese, "Do you think we can actually clear up this vhai hiouh tonight? Have the ehhifs stopped tampering with this sorry excuse for a worldgate?"

"It's still a mess," said Mmur'rr, "but a little more string manipulation should shut down the last remnants. Of course the ehhifs think it's already out of action."

"Next time be more careful," T'hsss hissed, materialising out of the darkness. The scarred black neutered Tom glared at him. "When you find loose strings you're supposed to report them, not play with them to see where they lead and open up your own gate!"

"How was I to know the ehhifs would spot it? I expected to end up in another yard, not superhero central!"

"No time for recriminations or bickering," said R'rrath. "Dig your claws in, find the strings, and let's get to work..."

**Notes for the Chapter:**

> The "Student who dropped out of sight in the nineties" is Winifred Burkle, from Angel. The British magician is John Constantine. "The last time they opened a portal it ended badly..." is a Buffy reference; see _Yesterday's Ghost_ for Kara's contact with the Buffyverse.
> 
> In the Young Wizards universe feline wizards have a special knack for handling worldgates; dimensional and temporal portals. Their claws allow them to manipulate dimensional strings directly. Opening gates randomly is frowned upon; you never know when or where they lead until you explore them. Vocabulary (from Diane Duane's _The Book of Night With Moon_ ):
>
>> Vhai - Damned  
> Hiouh - Excrement  
> Ehhifs - Humans


	3. Cat Chaser Chapter 1 - Director's commentary

**Summary for the Chapter:**

> There's currently a meme where fanfic writers are asked to add "commentary tracks" for stories, adding notes etc. One I was asked for was the first chapter of this story. The extra bits are bold and in square brackets **[like this]**

This is a DC Movieverse / DC Comics / Avengers (Movie) crossover. All characters belong to their respective creators, giant megacorporations of doom, etc. and there is no intent to infringe on copyright. The title is from a novel by Elmore Leonard. **[Who was a much better author than I am]**  
It may help if you've read the previous story, Five Dates Supergirl Didn’t Enjoy… And One She Did, which introduces several plot elements, but it isn't essential.

**Cat Chaser**

Part 1 **[this was original a single chapter story, but lots of people asked for more so I wrote another chapter, and added this subtitle]**

_Marcus L Rowland_

"Miss Potts."

Pepper turned away from the New York skyline and said "Yes, Jarvis?"

"There is a cat in laboratory four."

"What sort of cat?"

"A small brown one. It does not appear to be of any particular pedigree or breed. If it was a dog I would call it a mongrel."

"You're a snob, Jarvis. Okay... make sure it doesn't get into anything that will hurt it, I'll be down in a second. **[Why is the CEO of a multi-billion dollar company the person asked to deal with this? No idea... You'd think they'd have minions!]** Any sign of Tony?"

"Mister Stark is still en-route, ETA approximately eleven minutes."

Pepper descended to the laboratories and followed Jarvis' directions to a clear area, where one of Tony's industrial robots was keeping the cat busy with a laser pointer. She kneeled and said "Cut the laser. Hey, kitty."

The cat pretended to ignore her until she clicked her fingers, then it sidled towards her, and allowed her to stroke its ears and eventually pick it up. "Hey now, what's your name?" She noticed that it was wearing a collar, and looked at a small metal tag. "Pasadena Humane Society - My name is Streaky." On the back was a phone number.

"Jarvis, the tag has a phone number. I'm guessing it's a Pasadena area code, number 555 4389. That's odd..."

"It is. As you know, no Californian area includes 555 in the local dialling code." **[The old "put a 555 in the phone number so nobody gets weird phone calls" ploy strikes again, with extra lamplighting]**

"Where did he come from anyway?"

"I'm afraid I don't know. He appeared from under one of the work benches. I do not currently have a camera covering that area."

"Show me where."

The robot with the pointer beeped at her, then scooted across the floor towards one of the benches, as Jarvis said "I think we may have a problem." **[presumably JARVIS sees what the robot sees. Why he didn't do this earlier is anyone's guess.]**

"You're not kidding." Under the bench a vortex of rippling light, like a donut-shaped aurora about a foot across, hovered a few inches above the floor, inclined at about twenty degrees from the vertical. There was a scattering of earth below it. Through the opening she could see a slanted view of a neatly mowed lawn and some trees and bushes. She guessed it was a park or someone's back yard.

"The structure and signature of the energy field resembles that produced by the Tesseract... on a smaller scale, of course."

"Put me through to Tony."

"Hello, you have reached the helmet of Tony Stark, boy genius. Please leave a message. Beeeeep." **[I think there's something like this in one of the Iron Man films, forget which one. It seemed like his sort of humour anyway.]**

"Yeah, like that works so well. Tony, we have a problem."

"We're broke? You're pregnant?"

"Nope to both. But you do have a new baby here."

"What sort of baby?"

"Some sort of mini-portal, it's under a bench in one of the labs."

"Jarvis, give me some video... hey, cool!"

"It appears to be expanding," said Jarvis, "the diameter was thirty-two centimetres when I first saw it, it's now thirty-four point seven."

"Where is this in relationship to the original matrix portal?"

"Directly underneath it."

"The matrix generated its portal about a kilometre above the generator, can't remember the exact number."

"Twelve hundred and forty metres."

"About how far from it is the mini-portal."

"Approximately nine point seven metres below the generator."

"Give me a ratio between those distances."

"Ignoring the margin of error, the ratio of distances is exactly one hundred and twenty eight to one. By the way, the portal is now nearly forty centimetres across, and the rate of expansion is slowly increasing. It will intercept the floor and the surface of the bench in less than a minute. I suspect that it will damage them."

"Okay... I think it's a harmonic of the original portal, smaller and probably opens out somewhere a lot closer to home." **[Technobabble for the win!]**

"We just found a cat that seems to have walked through from Pasadena."

"Pasadena California? How far is that... okay, can't see an obvious connection." **[because I couldn't be arsed to work everything out to produce one]**

"It may not be this world's California," said Jarvis. "The phone number on its collar does not correspond to any local code in current use."

Outside Pepper heard a sonic boom, and braced herself for another argument with the FAA. Moments later **[or as long as it takes to get out of the armour, e.g. half a minute or so]** there was a clatter outside and Tony ran in, wearing his usual slacks and a Discworld T-shirt, the glow of his arc reactor nicely centred under the disc. **[if I had a glowy chest I'd look for fun T-shirts to go with it. Discworld, Death with the blue eyes, etc.]**

"Cool portal! Where's the cat?"

"Are you suffering from some optical deficiency?" asked Jarvis.

"Here," said Pepper, holding up the cat, which looked at Tony in disdain.

"Great, let's see what makes him tick."

"Over my dead body."

"Don't worry, I won't hurt him, just a few sensors. Jarvis, is Pepper being horribly irradiated even as we speak?"

"If she were, I think that I would have remembered to mention it."

"That's a no, I hope. Anything weird about it?"

"It appears to be an ordinary cat. However, I'm detecting occasional anomalous quantum events."

"And?"

"I was under the impression that you were the genius." **[My version of JARVIS is even more sarcastic than the film version]**

"Did we see anything like that with Thor or Loki?"

"No. By the way, the upper edge of the portal is about to come into contact with the power line to the bench. Should I shut it down?"

"Go for it."

"Done. It will be several minutes before the bench collapses."

"Okay, is Bruce around?"

"He's on his way up."

"Good - I think we need to get this thing out of here before it brings down the building."

"That does sound unusually prudent. For you."

* * * * *

"I think we can move it," said Bruce Banner. "The trouble is that if we do, we may change where it opens too." **[imagine a lot of SCIENCE! represented by that line of asterisks]**

"You mean the dimension Loki's storm-troopers came from? That would be bad."

"Possibly, or maybe Asgard itself."

"Excellent! Let's try for sideways out of the window then up, say a few metres above the roof, that shouldn't be too tricky."

"How do we get Streaky home if we do that?" asked Pepper.

"Quickly," said Bruce. "I want to take some more readings, but the events we're seeing could be caused by quantum entanglement."

"What does that mean?"

"I'm guessing that the cat comes from a fairly close worldline, maybe there are only a few minor differences. If I'm right it exists in both worlds, and there's quantum entanglement between the particles of the two versions now it's in our world. That's not really sustainable, so the entangled particles will vanish randomly from one or another cat. Eventually both of them will be damaged so badly that they die."

"How long have we got?"

"At the moment it's slow, it'll be hours before there's any harm. Say twelve hours for real damage, eighteen to kill both cats."

"You've got thirty minutes," said Pepper. "After that he's going back."

"But.."

"Twenty-five. We are not going to hurt a cat." **[Does canon Pepper like cats? I have no idea. My head canon version is a cat-lover.]**

"What happened to twenty-nine through twenty-six," asked Tony.

"Trying for fifteen?" asked Pepper.

"Fine," said Tony. "Bruce, I'll see to moving the portal, you see what you can find out from the cat, then give me a hand. Pepper, get the others in, if this goes horribly wrong we'll probably need backup."

* * * * *

Natasha dangled a small cuddly toy in front of Streaky's nose and made "good boy" noises, while Pepper stroked him and tried to keep him from moving from the focus of a small battery of sensors.

"Any luck with Selvig and his team?" asked Tony.

"They're at the Arecibo radio telescope in Puerto Rico," said Pepper. "They had a hurricane through there three days ago, communications are currently lousy, I can get you a voice link but that's about it." **[again, this should be a minion - blame it on me trying to keep the cast small]**

"Keep it as an option, but we'll try to handle it without him."

"Okay," said Bruce. "I think that's about it. There's an escalating pattern of quantum events, I'd say it was the beginning of an exponential series, a cascade of decaying particles. Make it six hours to significant damage, ten or twelve to death."

"Call it entropic cascade failure. It'll sound snappier when we write the papers and file the patents. **[yes, I stole the idea from Stargate]** Anything else we can learn from our feline friend?"

"Not really. Natasha, gently toss him back through the portal, but don't put your hands too close, we don't want you to get sucked into the world without shrimp or something."

"Without shrimp?" asked Captain America.

"Obscure geek reference, don't worry about it." **[since this series includes Buffy as one of the crossovers, and that's where the World Without Shrimp thing comes from, that got a lot of people wondering. Let's just say it's a common philosophical idea in both universes.]**

Natasha said "хороший кот" and tossed him towards the opening. He hit the portal and hung in mid-air, then bounced off and landed on the workshop floor, yowling, his fur bristling with rage.

"That's weird," said Tony. "Someone get a broomstick or something, give the portal a poke."

"I think that there may be higher priorities," said Jarvis. "In four minutes the lower edge of the portal will intersect one of the girders supporting this floor. I think that this might have unfortunate consequences."

"Get it out of here," said Steve. "We can solve the cat problem a lot easier if the building isn't collapsing."

"Okay," said Tony. "I think I can give it a little nudge, maybe move it up a few inches. Everyone stand well clear." He tweaked a couple of settings on the jury-rigged assembly of electromagnets and lasers he was working on, and switched on the power. For a few seconds nothing happened, then the portal disappeared.

"Was that supposed to happen?" asked Steve.

"No. Jarvis, what the hell just happened?"

"The portal re-located."

"Dare I ask where?"

"Approximately twelve hundred and forty metres above the tower. It is now considerably larger, incidentally; I'd estimate four to four point two metres in diameter, and it appears to be leaking water."

"I'd better get up there and take a closer look."

* * * * *

"What do you see, Tony?" asked Bruce.

"Okay, I'm just coming up level with the opening now... same scenery as before, looks like the new improved portal just sliced through a water pipe on the other side. I make that a couple of liters a second."

"Okay, I've got it on the monitor. Seems to be a lot of interference though. Try firing a repulsor burst at the portal, see what happens."

"Okay... a low-power shot has no effect... let's take it up a notch." Tony fired again, with enough force to knock down a small tree. On the far side of the portal the ground erupted, forming a shallow crater, and earth cascaded through the portal and onto Tony. **[Hey, let's commit an act of war against another dimension!]**

"I'd say that about twenty-five percent of the force is getting through," said Bruce.

"Sounds about right," said Tony. "I wonder what would happen if I fired a... holy crap!" He flew back from the portal, and was narrowly missed by a blue car that sped through and began to plummet towards the roof. He dove after it and grabbed the rear fender, which promptly tore off the back of the car. His repulsors threw him back up towards the portal as he struggled to regain control. **[I introduced a flying car (of sorts) in the previous story, naturally I used it again]**

About a hundred feet up the car started to slow, stopped, and rotated until it was more or less horizontal, then slowly descended to land on the roof. Tony landed as its occupants, a man and a woman, climbed out.

"Are you all right?" asked Tony.

"Apart from a missing fender," said the driver, an attractive blonde wearing jeans, running shoes, and a silky blue blouse. "I really wasn't expecting to run in to anyone up there. Oh, and hi, I'm Kara Zor-El."

"Dick Wing," said the passenger, a tall muscular brunet wearing a smart grey suit. **[Dick Greyson, who has learned lessons from Batman about not being too trusting with strangers]**

"Tony Stark."

"Hi. We're looking for Kara's cat."

"You have no idea who I am, do you?"

"Should we?" asked Kara.

"Just a second," said Tony, flipping open his visor. He lifted into the air, flew to his landing pad, and walked back towards them as the robotic arms stripped the armour from his body.

"That's amazing," said Kara. "How do you get the timing that accurate?"

"Genius, and massive parallel processing power," said Tony. **[he likes people who look beyond the suit and think about the other tech that goes with it]** "You're interested in engineering?"

"I'm studying it."

"And you've already built yourself a flying car? Look me up when you graduate."

"I'm pretty sure this isn't our timeline," said Kara, "so that might be kinda difficult."

"I'm certain of it," said Tony. "I'm pretty famous, so is my company. Stark Engineering. If you were an engineering student from around here you'd know me."

"Sorry," said Kara. "I guess it doesn't exist in our world."

"Okay. We've found your cat, if you'd like to follow me I'll take you to him. Jarvis, send a couple of the engineering robots up to fix their fender."

"Neat T-shirt," said Dick, "how do they get that glowing effect?"

"That would be me," said Tony, but didn't elaborate.

As they came down the stairs Jarvis said "Sir, I feel that you should be aware that the gentleman is carrying concealed weapons. Escrima sticks, several throwing stars, a small Taser, and something that looks like a grapnel gun, as well as various other devices. **[like I said, trained by Batman]** The young lady is unarmed." **[for definitions of unarmed that don't include being "more powerful than a locomotive" but Jarvis doesn't know that.]**

"Now he tells me," said Tony. "Okay, is this going to be a problem?"

"Not unless you make it one," said Dick. "I'm just here to help Kara find her cat, we don't want any trouble."

"Neither do we," said Tony. "What are you? Cop, gangster, bodyguard?"

"Vigilante," said Dick.

"Okay," said Tony. "Just so you know, there are probably at least four people here who can beat you up without working up a sweat. I'm not one of them, so watch out because I'll cheat if I have to."

"I'm not here to fight."

"We just want to get Streaky and take him home," said Kara. "Oh, and shut down that portal thing if it's yours, it's chewing up my back yard."

"So how does the car fly?"

Kara smiled. "Magic pixie dust. I caught Tinkerbell and waved her over the engine." **[it isn't the car that flies, it's Kara. She just has a very strong seatbelt!]**

"Do you mind if the robots look under the hood?"

"Knock yourself out."

"Everyone," said Tony, "These guys are Kara Zor-El and Dick Wing, they're here looking for Kara's cat. Kara's an engineering student, and Dick's in the vigilante business. Meet Natasha Romanoff, Clint Barton, Bruce Banner, Steve Rogers, and Pepper Potts."

"Hi!" "Pleased to meet you."

"Neither of you know any of those names?"

"Should we?"

"Okay, you really aren't from around here. That's weird, because if your time line is really distant we shouldn't be seeing quantum entanglement events, and your cat's showing them."

"Where is Streaky anyway?" asked Kara, looking around the room.

"Didn't you have him?" Pepper asked Natasha.

"I haven't had him since we tried to put him through the portal."

"That might be difficult," said Kara, "the last time I ran into a dimensional portal it carried a big energy charge, I think that there are sometimes big differences in potential between different dimensions. Coming here is like going downhill, but you might have to pump in a lot of energy to get back through it." **[see the previous story, in which Dick arrived from another dimension]**

"That's why you needed the car," said Tony, "a Faraday cage to get you through the energy field."

"That and we needed transport. So... Streaky?"

"Who had him last?"

"Natasha had him," said Pepper, "then we moved the portal out of here in a hurry. Anyone seen him?"

"He's got to be here somewhere," said Bruce. "Wait a second, I can track his movements through his quantum signature. But I'll have to eliminate your signatures first."

"What do we do?" asked Kara.

"Just stay where you are while I calibrate the sensors... that's odd, neither of you is showing any significant entanglement events. Though I'm detecting some from the roof."

"What does that mean?" asked Dick.

"It probably means that you don't exist in this dimension, maybe some of the atoms in your body do, but less than I would expect. Which is odd because a doppleganger of your cat does, and your car does."

"That's quite likely," said Kara. "Dick is a refugee from another dimension, he's only been in my world for a few months. And if I'm around at all in this universe I'm probably a few light years away from Earth, wouldn't that prevent entanglement?"

"Yes, it propagates at light speed..." said Bruce, then said "Wait a second, doesn't that mean you're an alien?" **[busted!]**

Kara held up her hand in a Vulcan salute and said "klaatu barada nikto. **[see _The Day the Earth Stood Still_ ] **Take me to your leader." Clint and Natasha watched her warily.

"You're an alien?" said Tony. "Why do you look human? Here to impregnate all the men with your flesh-eating eggs? Shape changer?"

"I wish, shape changing would be useful sometimes. No, Krypton was seeded by aliens who abducted early humans from Earth, about a hundred and fifty thousand years ago. **[this is my canon and I think something like it is DC canon, not entirely sure how they explain it these days]** Nobody's entirely sure why they did it, or why our evolution didn't diverge more, but we're not that dissimilar to Earth's humans. In fact my cousin married a woman from Earth, they have a kid." **[not sure why she told them that, given she hasn't even given them her Terran name, presumably she's decided it isn't going to be a problem in another dimension]**

"How did you get to Earth?" asked Bruce.

"A space warp a lot like your portal the first time I visited Earth, a spaceship the second. But that was a long dangerous voyage in suspended animation, it nearly killed me. I don't recommend it." **[see the first story of the series]**

"Your people can do that and you're studying engineering? _Our_ engineering?"

"We're trying to introduce our science and technology to Earth, but unless we start out with Earth's technology and build on it carefully it might as well be magic, people try to use it without understanding it. That's already got people killed. One criminal idiot who thought he had a handle on it came close to destroying most of the eastern seaboard." **[Lex, of course]**

"Sensible policy," said Bruce.

"How do you stop people from helping themselves?" asked Clint.

"I'm just naturally persuasive," said Kara.

Behind her Dick raised his eyebrows and said "Riiight...."

"Now, about Streaky?"

"I'm on it," said Bruce. "The instrument readings aren't clear, I think he's got under the floor through the hole the portal made, but he's within thirty feet."

"Okay," said Tony. "Jarvis, use the systems I installed for cleaning out escaped laboratory specimens, but turn off anything that might hurt him."

"Laboratory specimens?" asked Dick.

"Intelligent slime moulds, things men was not meant to know, rats, that sort of thing. We're big on research here."

"What exactly is here?" asked Dick. "I was wondering, because this doesn't look like a commercial operation somehow."

"We're the Avengers," said Steve, "we're what the papers like to call a superhero team." It was obvious that he was uncomfortable with the term.

"We used to have some of those in my world," said Dick, "they can be fun, especially the Christmas parties, but they get a bit cumbersome if you get too many big egos in the mix." **[hello JLA!]  
**  
"No argument there," said Pepper. **[hello Tony!]**

"There isn't anything like that in my world," said Kara, "though we do have some superheroes. Can you imagine Batman and Hancock on the same team?" **[there are a LOT of crossovers in this series - don't worry about it.]**

"For about ten seconds before they killed each other," said Dick.

"Do either of those names ring any bells?" asked Tony.

"No," said Natasha.

"I have the cat isolated," said Jarvis. "He is under the floor, grid reference G-11."

"Underneath the particle accelerator?" said Tony, checking the layout on one of the ubiquitous screens.

"Is there a problem?" asked Kara.

"It weighs forty-eight tons, it's bolted down, and we'd need to disconnect about sixty cables to move it more than a couple of feet."

"And?"

"The quantum effects he's experiencing might damage him by the time we can get it moved."

"Which would be bad," said Kara.

"Bad for him, certainly," said Tony.

"And for us." Bruce turned the screen to face them. "There's something I forgot, the energy release. The entangled particles don't just disappear, they annihilate each other. It's a cascade effect, starting very slowly but increasing exponentially. Say your cat weighs four kilograms, two kilograms would eventually be converted to energy. It's being radiated as neutrinos, which is why I didn't detect them at first, they tend not to cause problems. But in the last few seconds before the reaction completes a few hundred grams of matter will be converted to energy. Even as neutrinos we're talking a blast of several kilotons, possibly even worst." **[no, I have no idea how he's detecting neutrinos in a lab, when we need a load of gear at the bottom of a mine shaft and serveral months to spot one. It's comic-book science, live with it]**

"Two blasts," said Kara. "You said there must be a cat like Streaky somewhere in this world, probably in your version of California, he could be anywhere and the same thing would be happening to him." **[it makes sense given the circumstances]**

"Bruce," said Tony, "we need to get him out of there now, and back into his own world. Can you do it without losing control?"

"No other option?"

"Not in the time we have available. Let me get suited up first."

"How long have we got?" asked Kara.

"My best guess is still an hour or so before he starts to get hurt, but I've revised downwards twice now."

"Kara..." said Dick. "Isn't there something you should be telling these guys?"

"I guess." Kara looked embarrassed.

"What exactly might that be?" asked Clint, suspicion in his voice.

"Well... it's probably easier if I show you. Can you cut the power to the particle accelerator?"

"Already done," said Tony, "I didn't want the radiation to hurt him."

"Okay," said Kara. She went to one of the massive anchoring bolts and gripped it between her fingers and twisted. The head tore off. "Oops."

"It's okay," said Tony.

"What Kara kinda forgot to mention," Dick said as she moved around the machine and removed or destroyed the bolts one by one, "is that Kryptonians are pretty strong."

"I'm getting that. What do you think, Bruce?"

"I'm jealous; the other guy could smash the thing if I hulked out, but I don't think I could do anything that delicate. Assuming I was in my right mind, of course."

"Okay," said Kara, dumping the last bolt on the floor a few seconds later. "how far do I have to lift it before you can get the floor panel out?"

"About a foot," said Tony.

"Can I do that without damaging the cables?"

"Maybe, not sure."

"Okay, let's give it a try." Kara bent her knees, put her hands under the main mass of the particle accelerator, and lifted. It went up, wobbling a little, until some of the cables were taut. The floor panel she was standing on dented slightly under her feet. **[probably a lot less than it should if she's using her powers to counter the weight - I should have had Tony notice that.]** "How's that?"

"Just a second," said Tony. "Steve, can you lift the next floor panel enough to slide it out from underneath?"

"Let me help," said Dick. The floor panels had recessed lifting handles; Steve and Dick grabbed them and pulled and the panel lifted up a little; straining as hard as they could they managed to pull it back a couple of feet before the cables got in the way.

"There he is," said Clint, pointing into the cavity under the panel. He reached in and tried to get a hand to Streaky, but there wasn't quite room for him to reach far enough through the narrow gaps between the cables.

"I've got this one," said Pepper. She kneeled by the opening and waved a small metal can towards Streaky. He snuffled and walked towards her, but stopped too far back for easy grabbing.

"Isn't that my caviare?" said Tony.

"It's a good cause."

"Can you hold the accelerator for another moment?" asked Natasha. "I think I can reach him now."

"I think so," said Kara. **[she can, she just doesn't want them realising how strong she really is]**

"Good." Natasha dropped to the floor and squirmed under the cables, snaking her torso under the bulk of the generator, and grabbed Streaky. Clint pulled her out.

"Now just slide the panel back and put the accelerator down again and we're okay," said Tony. Everyone else glared at him.

* * * * *

"You've got the cat," said Bruce, "and I've modeled the wind flow around the tower, it looks like the water and dirt that's falling through the portal will be thoroughly dispersed before there's serious breakdown of its entangled particles. The mass won't be concentrated enough for the neutrino flux to do any damage." **[not sure what happens in California, but never mind...]**

"Are you sure you can shut the portal now?" asked Kara.

"Positive," said Tony. "The way it behaved when we tried to move it told me what we were doing wrong. I can shut it down completely."

"Have you guys got everything?" asked Clint.

"We've got Streaky, you've put all the earth that you could vacuum up into the trunk, and I don't think we've left anything behind."

"Once this closes we probably won't be able to reopen it into your dimension," said Tony, "I'm pretty sure it linked to it randomly. Make sure you have all your belongings."

"We're fine," said Kara. "Buckle up, this is going to be a bumpy ride." She fastened her seat belt and started the engine; Tony noticed that the belt seemed to be thicker and stronger than a regular belt **[see above]** , and guessed that it had something to do with her strength. Dick waved, and the car rose into the air, wobbling slightly, and ascended in a spiral towards the portal.

Tony followed, all of his instruments trained on the car, looking for an energy signature that might explain how it flew. There was some sort of hyperspace flux **[technobabble!]** , but he couldn't imagine how any so-called pixie dust could generate the effect. Maybe nanobots? There was something about the way the car was flying that seemed a little off to him, but he couldn't quite figure it out. "Jarvis, did you find anything unusual in the engine compartment?"

"No, just standard components."

"What about the 'Magic Pixie Dust' she mentioned; any nanobots or strange chemicals, or the sort of energy signature we got from Asgard technology."

"No sir. I believe that she may have been joking." **[JARVIS is not an idiot]**

Ahead the car wobbled again and banked for its final approach to the portal, and hit the boundary at about 50 MPH then slowed as though it had run into something soft but strong, coming to a halt with the front two thirds in Kara's world, the rear wheels and trunk in Tony's, with the car's suspension caught on something. Tony flew up and pushed up and forward on the rear fender; the car lurched forward and back into Kara's world, and he stopped himself before following it and hastily backed off from the portal. Through it he glimpsed Kara and Dick get out of the car. Kara waved at him, and he waved back, then said "Bruce... shut down the portal."

"In five... four.. three... two... one..." There was a bright flash and the portal was gone.

**Epilogue**

"Just when exactly were you planning to tell me about your visitors?" asked Nick Fury.

Tony smiled at the screen and said "Why tell you? You've got bugs all through the tower, you knew as soon as I did."

"Did it occur to you that I might have experts who could help?"

"Really? You know someone who knows more about portals than my team?"

"Yes. Reminds me, you probably can't patent anything derived from entropic cascade failure. There are already several classified patents in that area."

"Tell me more."

"You don't have the need to know. **[Hello Stargate Command...]** Now about the alien... do these Kryptonians pose a threat?"

"She seemed okay, but she said their technology nearly destroyed the eastern seaboard. And she was really strong... maybe Hulk strong, without the turning into a green rage monster part. One reason why getting them out of here quickly seemed the best way to handle things."

"Any other abilities? And did you get anywhere on the flying car?"

"Yes to both. There was something odd about the way that car flew, I analyzed the video and eventually realised that when it changed direction it was pivoting around the driver's seat, not the car's centre of mass. The car wasn't flying, she was, she just brought the car along to give her boyfriend a ride. I'm still figuring out how it works, but with luck it's something I can duplicate. Knowing that it's possible is a good start towards a solution."

"Interesting..."

"Now if there's nothing else, I need to make sure that Jarvis has flushed out the last of the cat poop from under the lab floor. We've got about twenty minutes before the cascade really gets started, I'd really like to make sure it's well clear of New York and harmlessly diluted first."

"Carry on. Fury out." His picture disappeared, replaced by a picture of Natasha holding Streaky captioned 'I has a Natasha.'

"Asshole," said Tony.

"He can still hear you, you know," said Pepper.

"And he's still an asshole. Now, about that cat poop..."

* * * * *

"They seemed like nice guys," said Linda Lee, as they walked back into her house. "Maybe we could have given our civilian names. But there were one hell of a lot of weapons around that building, and cells even I might have had trouble getting out of. And cameras everywhere, it was like _1984._ If we do exist in that world, I really don't want them knocking on our door."

"I think they were a government-sponsored superhero team," said Dick Grayson. "I've never heard of one of those that ended well. Stark and Banner were their scientists, I'm guessing that Barton, Romanoff and Rogers were muscle. Rogers was pretty strong, well over normal human levels, all three of them moved like they had combat and martial arts training."

"I've seen Romanoff's picture in our world. She's on the 'Ten Most Wanted' wall at NCIS headquarters, arms trafficking and murder. **[I have no idea why this is there, except that Gibbs likes redheads. I may do something with it, but I doubt it.]** I don't know any of the others."

"Give the names to Bruce... our Bruce... **[Wayne]** maybe he can track them down."

Outside Streaky yowled, and Linda's dog started to bark. "Now what?"

Another portal was opening a few feet above the lawn. As they watched a man fell through and landed, crouched, on the lawn. The portal slammed shut, and the man stood, a bearded blond giant holding a huge hammer, and said "Well met, fair maiden. I am Thor. Couldst thou tell me whether this be Midgard, and where I might find the abode of those known as the Avengers?"

"Now that might be tricky," Linda began. She had a feeling it was going to be one of those days...

**End of Part 1**   
**[originally The End, but a lot of reviewers wanted more - chapter 2 is the "Thor on Linda's world" story]**

Entropic Cascade Failure is stolen from Stargate SG-1. I've changed its effects considerably, the technobabble shouldn't be taken too seriously. The World Without Shrimp is a Buffy reference; in this universe (which has Buffy crossovers in previous stories) it is presumably a common philosophical concept. Natasha's Russian means "Good cat." Thanks to EllandrahSylver who gave me Thor's dialogue when I wasn't quite sure how to talk like an Asgardian.


End file.
